The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. However, these advances have increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing are needed. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component that can be created using a fabrication process) has decreased.
The decreasing geometry sizes may lead to various manufacturing difficulties. For example, a tri-layer structure is commonly used to pattern layers in semiconductor processes. However, as the device sizes become smaller and smaller, the use of tri-layer structures may cause over etching or under etching of structure layers, which may degrade semiconductor device performance or even lead to device failures.